1. Field of the Invention
The present invention relates to a melting furnace having a gas supplying apparatus, and more particularly, to a melting furnace having a gas supplying apparatus in which gas, particularly, for example, oxygen is provided to control a redox state of a vitrified molten material and stir the molten material to increase a processing capacity.
2. Description of the Related Art
It is highly important to safely dispose, store, and manage waste, particularly hazardous waste such as radioactive waste. One method for disposal and storage of the waste is vitrification, which disposes the waste by using glass. In this method, the waste such as the radioactive waste, slurry, contaminated ground, or industry waste is embedded in a glassy matrix such that the waste is not exposed to a surrounding environment and is permanently isolated.
Generally, in order to vitrificate waste, a waste vitrification apparatus melt a glass formation agent and the waste in a melting furnace, wherein a volatile component of the waste is exhausted through a waste treatment process of an exhaust gas and a toxic substance such as radionuclide or heavy metal remains for a certain time in which the toxic substance is heated to become a part of a glass network structure until a uniform mixture of molten glass is formed. The molten glass is discharged to form vitrified waste.
Generally, the melting furnace may use various heating methods and a cold crucible induction melter (“CCIM”), which uses induction heating, is configured to include a melting chamber of a cylindrical shape in which an electrical insulator is filled among a plurality of metal sectors, each of which has coolant circulating therein, and a high-frequency induction coil, provided outside of the melting chamber. A material, for example, waste and glass in the melting chamber is melted by high-frequency current applied to the induction coil. For example, Korea Patent No. 10-0501640, issued on Jul. 6, 2005, discloses “Method and Device for Incineration and Vitrification of Waste, in particular Radioactive Waste.”
Specifically, FIG. 1 is a view illustrating a configuration of a general inductive heating vitrification apparatus. In a chamber 10 comprising a plurality of metal sectors each of which is electrically insulated from one another has a cooling passage 12 formed therein, cooling water is circulated along the cooling passage 12 through pipes 12a and 12b connected to an external cooling water circulation system so that the entire chamber 10 maintains an appropriate temperature.
Glass within the chamber 10 maintains a molten state by high frequency current applied to an inductive coil 20 provided outside the chamber 10 and combustion gas among waste D injected through a waste supplying apparatus 30 is discharged to an exhaust gas processing apparatus through an exhaust unit 40. Molten glass is discharged outside through a discharging unit 50 provided in a lower portion of an exhaust hole 51.
A first oxygen supplying apparatus 60 is provided in proximity of the waste supplying apparatus 30 in an upper portion of the chamber 10 and oxygen supplied through the first oxygen supplying apparatus 60 optimizes combustion of the injected waste.
Meanwhile, in the low temperature melting furnace, when internal molten material does not include a bubble due to an influence of water cooling of a wall and a bottom surface of the melting furnace, a significant temperature difference exists inside the molten material. In this case, viscosity of the melting glass also has a wide distribution, and accordingly, a flow of the molten glass may not be effective due to a difference in viscosity such that the waste injected for vitrification may not be transmitted to an entire area of the molten glass. In such circumstance, uniform molten glass is difficult to produce and a waste processing rate may be reduced. Particularly, in the inductive heating low temperature melting furnace (or cold crucible induction melter), an operative problem may occur such that an arc in the metal sector may be generated due to a metal material formed in a lower portion of the chamber.
To avoid this problem, a second oxygen supplying apparatus 70 for supplying oxygen is provided in the lower portion of the chamber 10 to generate the bubble in the molten glass.
FIG. 2 is a view illustrating an oxygen supplying apparatus provided in a conventional vitrification apparatus. The oxygen supplying apparatus 70 includes a casing 71 that penetrates the lower portion of the chamber to be fixed, an oxygen supplying pipe 72 provided within the casing 71 to supply oxygen into the chamber 10, and a cooling water inlet pipe 73 and a cooling water outlet pipe 74 for circulating the cooling water.
An exhaust hole 72a is formed on an upper portion of the oxygen supplying pipe 72 so that the oxygen supplied from the oxygen supplying pipe 72 is introduced to the chamber 10 through the exhaust hole 72a to produce the bubble in the molten glass.
However, in the conventional oxygen supplying apparatus, an oxygen supplying pipe, and the cooling water inlet pipe and the cooling water outlet pipe for circulating the cooling water are fixed and supported by a separate casing and requires a cooling water pipe for cooling the oxygen supplying pipe separately from a cooling water circulation system for cooling the wall of the chamber 10, thereby adding complexity to the structure as well as causing difficulty in repair when breakdown occurs and inconvenience in maintenance.